Display screen or portion thereof having a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof having a graphical user interface, showing my new design, in accordance with a first embodiment thereof; and,

FIG. 2 is a front view of a display screen or portion thereof having a graphical user interface, showing my new design, in accordance with a second embodiment thereof.

Subject matter shown in broken lines, including the display screen and the remainder of the graphical user interface, is included for the purpose of illustrating environmental structure, and the broken lines form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof having a graphical user interface, as shown and described. 